Deadly drownings of animals in water canals for irrigation and other purposes have been observed in various countries. The dry and semiarid regions of the planet are even more vulnerable to these losses, but there are alternatives to protect wildlife.

Scientists like Diego Gallego-García came across wildlife drowned to death in and around an irrigation and water supply canal while researching birds in northern Argentina. The losses recorded were striking.

More than 200 animals from 35 species died in six months, according to a study in the journal Biological Conservation authored by Gallego-García and José Sarasola, both from Argentina’s National Council for Scientific and Technical Research (CONICET) and the National University of La Pampa.

The drownings occurred in the Canal de la Patria, whose steep concrete walls cut through 250 kilometers (155 miles) of the Gran Chaco region. This is the most biodiverse continuous forest system in South America after the Amazon Rainforest.

The victims represent a range of species, including threatened ones, such as 38 giant anteaters (Myrmecophaga tridactyla), a large ant and termite eater typical of South American savannas.

The study also recorded that the number of animal deaths declined over the months analyzed, but this signals something even more serious.

“We may be witnessing a defaunation [rapid extinction of wildlife] process along the canal. This is very serious for the conservation of wildlife species and a problem that has so far been kept silent,” Gallego-García says. The damages are likely widespread across the country but have not been assessed.

There are at least 6,000 km (3,700 mi) of canals cross Argentina’s arid and semiarid areas. The damaged concrete of these structures is often replaced by slippery plastic tarpaulins, which make it harder for animals to escape. This reinforces their role as “wildlife traps,” the researchers warn.

Globalized drownings

Fatal drownings of animals also occurred in an irrigation system just 1.5 km long, or less than a mile, connected to the protected wetland area Bordo Las Maravillas, in the municipality of Toluca, Mexico.

A study published in the journal PeerJ documented 227 drowned animals from a dozen different species, including birds, amphibians and, especially, mammals and reptiles. The survey ran for two years.

At the site, canals with rectangular concrete walls are controlled by sluices, where animals also end up getting trapped, says study co-author Hublester Domínguez-Vega.

“The system is small, but it has a high impact on so many species,” says Domínguez-Vega, who holds a Ph.D. in agricultural sciences and natural resource management from the Autonomous University of Mexico State (UAEM).

He says there’s a widespread lack of understanding worldwide about how the construction and operation of water canals affect biodiversity. “We are only scratching the surface of these issues,” he says.

Native to the Sonora Desert of Mexico and the United States, the Sonoran pronghorn (Antilocapra americana sonoriensis) is the fastest land mammal in North America, reaching speeds of 80 km per hour (50 mi per hour). However, this hasn’t spared it from drowning in water canals.

The drownings were recorded by Paul Krausman, a professor of wildlife and fisheries sciences at the University of Arizona and one of the few researchers studying such impacts on wildlife.

His studies show the deaths of deer and other animals in systems like the All-American Canal. It runs 130 km (80 mi), connecting Imperial Dam on the Colorado River to nine cities and 2,000 km² (770 mi2) of irrigated land in California.

For Krausman, any loss due to drowning in canals harms biodiversity, especially for threatened species. “Canals are just one of many challenges animals face,” he says.

“If these damages are overlooked or unknown in other countries, it’s probably because they haven’t been studied,” he adds. The global area to be assessed is vast and continues to grow.

Global irrigation covers between 2.55 million and 3.05 million km² (965,000 and 1,160 million mi2), an area nearly the size of India. These figures are from the United Nations’ Food and Agriculture Organization.

In Europe, the situation seems no less fatal for wildlife than in the Americas.

Scientific studies reported 538 wild and domestic mammals drowned in canals in Spain over a period of five years, and also indicated that amphibians are the main victims of these structures.

Other studies identified drowning in water canals as the second leading cause of unnatural deaths for wild boars (Sus scrofa) in Spain. The first is vehicle collisions.

In Los Payuelos, a canal in Spain’s northwestern León region, repeated drownings of roe deer (Capreolus capreolus) have been recorded. In one incident a few years ago, 28 of these animals died.

Drownings have also occurred in the Arriola and Villalaco canals in central-northern Spain. Similar structures are found throughout the country, for irrigation, water supply or transportation.

Smaller species are the most affected by these systems, says Alberto Fernandez Lopez, from WWF-Spain’s water program. “There is a lack of research and serious action on the issue,” says Lopez, who holds a Ph.D. in biology from Complutense University of Madrid.

Neighboring Portugal’s canals have also proved to be deadly for wildlife.

A study published in the journal Basic and Applied Ecology drowned mammals, including carnivores, in seven canals in the south of the country, each of which runs an average 12 km (7.5 mi).

The victims include the common genet (Genetta genetta), European polecat (Mustela putorius), Egyptian mongoose (Herpestes ichneumon), Eurasian otter (Lutra lutra), Eurasian badger (Meles meles), and the red fox (Vulpes vulpes).

The deaths occurred despite the concrete canals being theoretically isolated by wire fences 1.5 meters (5 feet) high, with an additional 0.5 m (1.6 ft) stretching underground.

“The results are relevant as more irrigation canals are being built to cope with increased droughts and greater demand for food,” say the study authors from Évora and Lisbon universities in Portugal.

There’s more than 37,000 km² (14,2o0 mi2) of irrigated land in Portugal and Spain, according to the FAO, or an area half the size of Panama.

Connecting the dots

Roadways, railways and artificial water canals complicate animal movements and cause fatalities through collisions and drownings. Their “barrier effect” can also isolate populations, compromising reproduction and food access for wildlife.

“Road damage is much more visible. People drive by and can see many of the dead animals,” says Edgar van der Grift, a researcher at the Department of Animal Ecology at Wageningen University & Research in the Netherlands.

The situation suggests that reducing animal mortality and the negative impacts on biodiversity conservation in water canals will require intense scientific, legal, technical and economic efforts, as well as urgent actions from governments worldwide.

“Although canals are one of the leading causes of direct wildlife mortality, they receive little attention,” says UAEM’s Domínguez-Vega.

The problem is growing alongside the global trend of increasing artificial irrigation to produce food in response to population growth and the accelerated effects of the climate crisis, such as reduced rainfall, higher temperatures, and droughts.

“Savannas are more susceptible to these impacts and greater harm to wildlife,” says Morati Mpalo, from the Department of Earth and Environmental Sciences at the Botswana International University of Science and Technology.

Mpalo is one of the authors of a study published in the journal Land, indicating that artificial water sources not only drown wildlife but also disrupt natural environments. The study focused on the Chobe Enclave in the northern part of Botswana.

“This continuous water supply disturbed a drought-sensitive landscape, affected wildlife and the heterogeneity of vegetation, indicating it causes ecological changes in savannas,” Mpalo says.

Rodrigo Gerhardt, from the NGO World Animal Protection in Brazil, says the cumulative ecological damage caused by irrigation systems is a “global scandal” that “needs to come out of the shadows.”

“The cost of neglecting the damage caused by this activity is showing up in the deaths of countless native and domestic specimens, in the imbalance of ecosystems, and in the worsening of the climate crisis,” he says.

Overcoming impacts

Gallego-García, from Argentina’s national research council, says the only real solution for wildlife is to completely cover these water canals.

“It is an urgent issue. They are silent killing machines for wildlife, still greatly underestimated worldwide,” he says.

Covering open canals would also reduce the barrier effect, a problem that can be reinforced by other means of containing animal drownings, such as fences alongside structures that could stretch for hundreds of kilometers.

“Bridges, tunnels and ditches help animals cross water canals, but they are not used by all species and are not effective solutions for preventing deaths and the fragmentation of natural habitats,” Gallego-García says.

Krausman from the University of Arizona says it’s equally possible to facilitate the exit of animals from artificial water canals and reservoirs.

“Ramps, animal ladders and structures with abrasive walls allow many animals that have fallen to escape death,” he says.

In this regard, attempting to save animal lives in both artificial and natural watercourses is a policy adopted in the Netherlands, a country crisscrossed by canals used for irrigation, public water supply and navigation.

“The impacts of the canals may seem small, but drownings of species with smaller populations can severely affect their conservation,” says Wageningen’s Van der Grift.

In the Netherlands, water canals are equipped with speed reducers and ramps to facilitate the exit of wildlife, domestic animals and even people. “They are installed along both sides of the canals,” Van der Grift says.

Domínguez-Vega says mitigating the damage caused by open-air irrigation canals requires thorough assessments in each region and may even involve redesigning the canals to minimize harm to animals.

“Greater knowledge is needed before any measures are taken, so as not to pursue short-term agendas with false solutions,” he says. “However, there is no single solution to the lethality of the canals.”

This is a scenario that calls for a reconsideration of irrigation practices worldwide, in order to balance the socioeconomic benefits of the activity with the protection of habitats and native species.

“Advocating for proper use does not mean being against irrigation. Agriculture and other activities can use water without killing wildlife,” Gallego-García says.

As of the time this story was originally published, the governments of Mexico, Argentina, Portugal, Spain and Botswana hadn’t responded to whether they monitor or take action to prevent fatal drownings of wildlife in irrigation canals and other water channels in their respective jurisdictions.

The U.S. Fish and Wildlife Service says there are proposals to install nets and alerts in navigation locks and other water controls in Florida and Puerto Rico to reduce collisions, injuries and crushing of the endangered manatee.

This article was first published here by ((o))eco on Feb. 6, 2025.

Banner image: A giant anteater (Myrmecophaga tridactyla) trapped in a water canal in Argentina. Image courtesy of the Center for the Study and Conservation of Birds of Prey in Argentina (Cecara)